On Fri, Jun 20, 2014 at 08:12:59AM +0200, Attilio Rao wrote: > On Fri, Jun 20, 2014 at 6:08 AM, Konstantin Belousov > <kostik...@gmail.com> wrote: > > On Thu, Jun 19, 2014 at 09:54:41PM +0000, Attilio Rao wrote: > >> Author: attilio > >> Date: Thu Jun 19 21:54:41 2014 > >> New Revision: 267651 > >> URL: http://svnweb.freebsd.org/changeset/base/267651 > >> > >> Log: > >> Following comments in r242565 add the possibility to specify ecx when > >> performing cpuid calls. > >> Add also a new way to specify the level type to cpucontrol(8) as > >> reported in the manpage. > >> > >> Sponsored by: EMC / Isilon storage division > >> Reviewed by: bdrewery, gcooper > >> Testerd by: bdrewery > >> Modified: head/sys/sys/cpuctl.h > >> ============================================================================== > >> --- head/sys/sys/cpuctl.h Thu Jun 19 21:05:07 2014 (r267650) > >> +++ head/sys/sys/cpuctl.h Thu Jun 19 21:54:41 2014 (r267651) > >> @@ -35,7 +35,8 @@ typedef struct { > >> } cpuctl_msr_args_t; > >> > >> typedef struct { > >> - int level; /* CPUID level */ > >> + int level; /* CPUID level */ > >> + int level_type; /* CPUID level type */ > >> uint32_t data[4]; > >> } cpuctl_cpuid_args_t; > >> > >> @@ -50,5 +51,6 @@ typedef struct { > >> #define CPUCTL_UPDATE _IOWR('c', 4, cpuctl_update_args_t) > >> #define CPUCTL_MSRSBIT _IOWR('c', 5, cpuctl_msr_args_t) > >> #define CPUCTL_MSRCBIT _IOWR('c', 6, cpuctl_msr_args_t) > >> +#define CPUCTL_CPUID_COUNT _IOWR('c', 7, cpuctl_cpuid_args_t) > >> > >> #endif /* _CPUCTL_H_ */ > > > > The cpuctl(4) is used by third-party code, and this change breaks its > > ABI. The numeric value for CPUCTL_CPUID is changed, which means that > > old binaries call non-existing ioctl now. This is at least a visible > > breakage, since the argument for the ioctl changed the layout as well. > > > > The following patch restored the CPUCTL_CPUID for me. I considered > > naming its argument differently, instead of renaming the argument > > of CPUCTL_CPUID_COUNT (which you tried to do ?), but decided not, > > to preserve the API as well. > > No, breaking the ABI is fine for -CURRENT so I don't see why we need the > bloat.
No, breaking ABI is not fine at all, be it CURRENT or not. We try to keep the ABI stable, doing costly measures like symbol versioning, where applicable. Since this is a change to ABI for kernel interface, it cannot be covered by symver tricks and must be done in kernel. > I don't plan on MFC this patch. If I need to (or any user requests > that) I will do with the appropriate ABI-compliant way (ie. adding a > new argument like this one). Besides the same-world ABI issue, people run jails with lower world version on higher-versioned kernels.
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